The present invention relates to a thyristor with pressure contacting in which at least a portion of the control base zone in addition to the cathode zone borders on one major surface of a semiconductor wafer-shaped thyristor element and the cathode and control base zones each are contiguous and are provided at least in part with completely insulated ohmic electrodes (cathode and control electrode) at this major surface.
German Auslegeschrift (Published Patent Application) No. 1,209,207 discloses a controllable semiconductor rectifier with the above-described structural features and an npnp semiconductor body in which part of the zone which borders on the cathode zone, here called the emitter zone, and constituting the control base zone extends through this emitter zone to the surface of the semiconductor body, this part of the control base zone being provided with an ohmic electrode at the surface of the semiconductor body. The surface of this penetrating portion of the control base zone forms a contiguous strip pattern on the surface of the emitter or cathode zone which is distributed over the entire surface of the emitter or cathode zone so that the area of the strip pattern is smaller than the area of the emitter or cathode zone at the surface of the semiconductor body and is covered by the ohmic electrode. The strip pattern may be formed as a plurality of interconnected fir-tree patterns which radially outwardly extend from the center of the major surface or as a plurality of strips which intersect at right angles in the shape of a net.
In the known controllable semiconductor rectifier, the surface of the emitter or cathode zone and the ohmic electrode attached thereon are situated lower than the strip pattern of the control base zone including the above-mentioned ohmic electrode with which the strip pattern of the control base zone is provided and the entire surface of the emitter or cathode zone and the ohmic electrode applied thereto are contacted with an electrically conductive material, for example in the form of a wafer or disc. In order to prevent the ohmic electrode of the strip pattern of the control base zone, which lies higher than the ohmic electrode of the emitter or cathode zone from also being contacted by this wafer or disc, it is necessary, however, for this wafer or disc to be provided at its contacting surface with a negative pattern with respect to the strip pattern of the control base zone which negative pattern can be produced only with extreme care and great difficulty.